1. Field of the Invention
The present invention relates to display units used with cryptography technologies, and more specifically to a method and apparatus for storing and using a cryptography key.
2. Related Art
Display units are often used to receive and display data encoded in a display signal received on a serial communication channel. As used in the present application, display units contain both analog display units (typically based on cathode ray tube technology) and digital display units (typically based on flat panels). The display signal generally contains data representing image frames and synchronization signals (e.g., VSYNC and HSYNC) indicative of the line and frame boundaries.
It may be necessary to implement cryptography applications in display units. In a common cryptography application, underlying data is encrypted at a sending location and transferred to a receiving location. The encrypted data is then decrypted at a receiving end to recover the original data. Due to the encryption and decryption, an unauthorized third party may be unable to decipher (or even alter) the underlying data when the data is transmitted from the sending location to the receiving location.
One common application of cryptography is when a display unit needs to decrypt data encoded in a received display signal. The data is typically encrypted to avoid illegal copying of the data when the display signal is being transmitted. For example, a graphics controller of a computer system may encrypt data representing image frames and send the encrypted data in a serial communication channel, and it may be necessary to decrypt the data in the display unit so that the image frames can be displayed.
Keys are commonly used in cryptography. Examples of such keys include an encryption key used to encrypt data, a decryption key to decrypt the data, and an authentication key to authenticate the source sending data. Details of guidelines (standards) for implementation of cryptography are provided in further detail in a document entitled, “High Bandwidth Digital Content Protection System, Revision 1.0” dated Feb. 17, 2000, and available from Digital Display Working Group (DDWG), which is incorporated in its entirety herewith.
Preventing unauthorized access to keys used in cryptography is often important. For example, the encrypted data can often be decrypted by an unauthorized party if the party has access to the decryption key. Therefore, what is needed is a method and apparatus which prevents (or substantially discourages) unauthorized access to keys.